1. Field of the Invention
The present invention relates to an image forming method and an apparatus therefor and, more particularly, to the image forming method and apparatus suitable for image formations by the electrophotography.
2. Description of the Prior Art
In recent years, there appears an image forming apparatus for making full-color copies by using a full-color original image (or document) in the image forming by the electrophotography. The multi-color image is very favorable not only for reproducing pictures of figures, still lives, landscapes and so on but also for diagrams, tables and so on because one recorded image can incorporate many pieces of informations.
From the circumstances described above, there have been proposed a variety of methods of and apparatus for forming the multi-color images.
In one method (as is disclosed in Japanese Patent Laid-Open Nos. 106743/1977, 144452/1981 and 79261/1983), for example, a plurality of latent image forming means and a plurality of developing means are arranged around a rotating drum-shaped photosensitive member, visible images of different colors are formed and superposed on the drum-shaped photosensitive member by repeatedly forming and developing the latent images and are transferred altogether to a sheet of recording paper.
In another method (as is disclosed in Japanese Patent Laid-Open Nos. 76766/1985 and 95456/1985), one latent image forming means and a plurality of developing means are arranged around a rotating drum-shaped photosensitive member to form and develop a latent image of one color for each rotation of the photosensitive member, and multi-color visible images are formed on the photosensitive member as a result of rotations of the photosensitive member and are transferred altogether to a sheet of recording paper.
In case the colors to be reproduced are full colors including yellow, magenta and cyan colors, and a black color, if necessary, according to the former method, the number of the latent image forming means and the developing means to be arranged around the photosensitive member is equal to the number of the kinds of the above-specified colors so that the photosensitive member has an increased diameter to enlarge the size of the apparatus.
According to the latter method, on the contrary, the apparatus can be made smaller than that of the former method because of the single latent image forming means. However, the photosensitive member has to make the same rotations as the number of the kinds of the colors so that the rate of forming the multi-color image is dropped.